Cutting edge: the membrane attack complex of complement is required for the development of murine experimental cerebral malaria

Cerebral malaria is the most severe complication of Plasmodium falciparum infection and accounts for a large number of malaria fatalities worldwide. Recent studies demonstrated that C5(-/-) mice are resistant to experimental cerebral malaria (ECM) and suggested that protection was due to loss of C5a-induced inflammation. Surprisingly, we observed that C5aR(-/-) mice were fully susceptible to disease, indicating that C5a is not required for ECM. C3aR(-/-) and C3aR(-/-) × C5aR(-/-) mice were equally susceptible to ECM as were wild-type mice, indicating that neither complement anaphylatoxin receptor is critical for ECM development. In contrast, C9 deposition in the brains of mice with ECM suggested an important role for the terminal complement pathway. Treatment with anti-C9 Ab significantly increased survival time and reduced mortality in ECM. Our data indicate that protection from ECM in C5(-/-) mice is mediated through inhibition of membrane attack complex formation and not through C5a-induced inflammation.     

A Respiratory Syncytial Virus (RSV) Anti-G Protein F(ab′)2 Monoclonal Antibody Suppresses Mucous Production and Breathing Effort in RSV rA2-line19F-Infected BALB/c Mice

Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. Increased airway resistance and increased airway mucin production are two manifestations of RSV infection in children. RSV rA2-line19F infection induces pulmonary mucous production and increased breathing effort in BALB/c mice and provides a way to assess these manifestations of RSV disease in an animal model. In the present study, we investigated the effect of prophylactic treatment with the F(ab′)₂ form of the anti-G protein monoclonal antibody (MAb) 131-2G on disease in RSV rA2-line19F-challenged mice. F(ab′)₂ 131-2G does not affect virus replication. It and the intact form that does decrease virus replication prevented increased breathing effort and airway mucin production, as well as weight loss, pulmonary inflammatory-cell infiltration, and the pulmonary substance P and pulmonary Th2 cytokine levels that occur in mice challenged with this virus. These data suggest that the RSV G protein contributes to prominent manifestations of RSV disease and that MAb 131-2G can prevent these manifestations of RSV disease without inhibiting virus infection.     

Pyridine-3-propanoic acids: Discovery of dual PPARalpha/gamma agonists as antidiabetic agents

A series of novel pyridine-3-propanoic acids was synthesized. A structure-activity relationship study of these compounds led to the identification of potent dual PPARalpha/gamma agonists with varied isoform selectivity. Based on the results of efficacy studies in diabetic (db/db) mice, and the desired pharmacokinetic parameters, compounds (S)-14 and (S)-19 were selected for further profiling.     

Inferring the Evolutionary History of Mo-Dependent Nitrogen Fixation from Phylogenetic Studies of nifK and nifDK

The ability to fix nitrogen is widely, but sporadically distributed among the Bacteria and Archaea suggesting either a vertically inherited, ancient function with widespread loss across genera or an adaptive feature transferred laterally between co-inhabitants of nitrogen-poor environments. As previous phylogenetic studies of nifH and nifD have not completely resolved the evolutionary history of nitrogenase, sixty nifD, nifK, and combined nifDK genes were analyzed using Bayesian, maximum likelihood, and parsimony algorithms to determine whether the individual and combined datasets could provide additional information. The results show congruence between the 16S and nifDK phylogenies at the phyla level and generally support vertical descent with loss. However, statistically significant differences between tree topographies suggest a complex evolutionary history with the underlying pattern of vertical descent obscured by recurring lateral transfer events and different patterns of evolution between the genes. Results support inheritance from the Last Common ancestor or an ancient lateral transfer of the nif genes between Bacteria and Archaea, ongoing gene transfer between cohabitants of similar biogeographic regions, acquisition of nitrogen-fixing capability via symbiosis islands, possible xenologous displacement of one gene in the operon, and possible retention of ancestral genes in heterocystous cyanobacteria. Analyses support the monophyly of the Cyanobacteria, αβγ-Proteobacteria, and Actinobacteria (Frankia) and provide strong support for the placement of Frankia nif genes at the base of combined the Cyanobacteria/Proteobacteria clades.     

Excision of the <Emphasis Type="Italic">nifD</Emphasis> element in the heterocystous cyanobacteria

Heterocyst differentiation in cyanobacteria is accompanied by developmentally regulated DNA rearrangements that occur within the nifD, fdxN, and hupL genes. These genetic elements are excised from the genome by site-specific recombination during the latter stages of differentiation. The nifD element is excised by the recombinase, XisA, located within the element. Our objective was to examine the XisA-mediated excision of the nifD element. To accomplish this, we observed the ability of XisA to excise substrate plasmids that contained the flanking regions of the nifD element in an E. coli host. Using PCR directed mutagenesis, nucleotides in the nifD element flanking regions in substrate plasmids were altered and the effect on recombination was determined. Results indicate that only certain nucleotides within and surrounding the direct repeats are involved in excision. In some nucleotide positions, the presence of a purine versus a pyrimidine greatly affected recombination. Our results also indicated that the site of excision and branch migration occurs in a 6 bp region within the direct repeats. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Critical requirement of CD11b (Mac-1) on T cells and accessory cells for development of experimental autoimmune encephalomyelitis

Mac-1 (CD18/CD11b) is a member of the beta2-integrin family of adhesion molecules and is implicated in the development of many inflammatory diseases. The role of Mac-1 in the development of CNS demyelinating diseases, including multiple sclerosis, is not understood, and Ab inhibition studies in experimental allergic encephalomyelitis (EAE), the animal model for multiple sclerosis, have produced conflicting findings. To clarify these results and to determine Mac-1-mediated mechanisms in EAE, we performed EAE using Mac-1-deficient mice. Mac-1 homozygous-deficient, but not Mac-1 heterozygous-deficient mice, had significantly delayed onset and attenuated EAE. Leukocyte infiltration was similar in both groups of mice in early disease but significantly reduced in spinal cords of receptor-deficient mice in late disease. Adoptive transfer of Ag-restimulated T cells from wild-type to Mac-1-deficient mice produced significantly attenuated EAE, whereas transfer of Mac-1-deficient Ag-restimulated T cells to control mice failed to induce EAE. T cells from myelin oligodendrocyte glycoprotein (MOG)35-55 peptide-primed Mac-1-deficient mice displayed an altered cytokine phenotype with elevated levels of TGF-beta and IL-10, but reduced levels of IL-2, IFN-gamma, TNF-alpha, IL-12, and IL-4 compared with control mice. Mac-1-deficient T cells from primed mice proliferated comparably to that of control T cells on MOG35-55 restimulation in vitro. However, the draining lymph nodes of MAC-1-deficient mice on day 10 after MOG35-55 immunization contained lower frequency of blast T cells than in control mice, suggesting poor priming. Our results indicate that Mac-1 expression is critical on both phagocytic cells and T cells for the development of demyelinating disease.